1. Field of the Invention
The present invention relates to a subject-state detecting apparatus applicable to a vehicle for detecting the state of an occupant by using an active distance measuring method.
2. Description of Related Art
A subject-state detecting apparatus detects the presence or absence of a person within a measuring range or the frame and posture of a person in a sitting position using an optical sensor or the like. As for such an apparatus, Japanese patent application laid-open No. 9-309402 discloses a technique titled xe2x80x9cOccupant Judgement Device for Vehicular Air Bag Systemxe2x80x9d, for example. It relates to a configuration of an optical sensor that throws light from a light-emitting device on a subject by a mechanical scanning system, and detects the reflected light with a photodetector via the mechanical scanning system. The optical sensor is mounted on an upper side of a person to throw broad light beams onto the occupant in the vehicle, and decides a rough state of the occupant from the detected light. The occupant decision apparatus can decide whether an adult is sitting in a normal state, or a child is standing.
As another conventional technique of this kind, Japanese patent application laid-open No. 2000-241561 discloses a technique titled xe2x80x9cDevice and Method for Detecting In-Bed Statexe2x80x9d. It measures the heights of individual points of a subject by projecting light or ultrasound onto the subject from a light source or ultrasound source attached on a ceiling, and by capturing the reflected light or sound by a distance measuring sensor, thereby making it possible to detect the state of a person on a bed.
With the foregoing configurations, the conventional subject-state detecting apparatuses throw broad light beams onto the subjects, and hence can recognize only a rough state of a person. In addition, they have a problem in that they can detect only presupposed static states.
The present invention is implemented to solve the foregoing problems. It is therefore an object of the present invention to provide a subject-state detecting apparatus capable of detecting the state of a person accurately in such circumstances as the subject changes dynamically.
According to one aspect of the present invention, there is provided a subject-state detecting apparatus comprising: a distance measuring section that has an active distance measuring sensor including a plurality of projectors and a photodetector for detecting reflection light; a measurement parameter decision section for deciding a body parameter to be measured in advance; a distance measuring sensor setting section for setting the active distance measuring sensor and an additional distance measuring sensor in response to the body parameter; and a state decision section for deciding a state of the subject by analyzing detection outputs of the active distance measuring sensor and the additional distance measuring sensor. Thus, the subject-state detecting apparatus can give leeway to the variable number of the measurement points in advance. Accordingly, under the condition in which the subject to be measured moves dynamically, it offers an advantage of being able to carry out the optimum measurement in terms of the measurement time and accuracy by measuring only the fewest possible number of the measuring points to obtain the body parameter. Furthermore, it offers an advantage of being able to implement the optimum measuring sequence by controlling the distance measuring sensor system in its entirety which includes not only the active distance measuring sensors but also the additional distance measuring sensor to obtain the body parameter in response to the environmental conditions.